1. Field of the Invention
The present invention relates to a method and apparatus for supplying lead frames stored inside a magazine to a frame feeder in a bonding apparatus such as a wire bonding apparatus, die bonding apparatus and the like.
2. Prior Art
A conventional bonding apparatus is described with reference to FIGS. 4(a) and 4(b).
Loader side magazines 1 (1A, 1B . . . ) and unloader side magazines 2 (2A, 2B . . . ) are respectively positioned at both ends of the guide rails 11 of a frame feeder 10. These loader side magazines 1 and unloader side magazines 2 are positioned and carried on magazine holders which are respectively driven up and down by a loader side elevator 3 and an unloader side elevator 4. Lead frames 6 are stored in the loader side magazines 1 and pushed out onto the frame conveying path 11a of the guide rails 11 by a frame pusher 7.
Examples of bonding systems equipped with elevator devices of the type described above are disclosed in Japanese Patent Application Publication (Kokoku) Nos. S63-56122, H1-32127 and H2-4486.
The system described in, for example, Japanese Patent Application Publication No. S55-7944 shows no frame pusher 7 and instead includes a pull-in claw 8.
The conventional bonding apparatuses thus include either a frame pusher 7 or a pull-in claw 8; and the pull-in claw 8 is shown by a two-dot chain line in FIG. 4(a). In the apparatus that includes such a pull-in claw 8, the lead frames 6 inside the loader side magazines 1 are pulled by the pull-in claw 8 so as to be moved onto the frame conveying path 11a of the guide rails 11.
The frame feeder 10 which conveys the lead frames 6 includes a pair of guide rails 11, which have a frame conveying path 11 a that guides the lead frames 6, as well as loader side feeding claws 12 and unloader side feeding claws 13. The loader side feeding claws 12 and unloader side feeding claws 13 consist of respective pairs of upper claws 12a and 13a and lower claws 12b and 13b as best shown in FIG. 4(b). The loader side feeding claws 12 and unloader side feeding claws 13 are opened and closed by claw open/close means (not shown) and are caused to move along the guide rails 11 by a claw moving means (not shown). Furthermore, a frame confirmation sensor 14 which detects the presence of a lead frame 6 is installed between the guide rails 11 so as to be on the side of the loader side magazines 1.
This type of the frame feeders 10 are described in Japanese Patent Application Publication (Kokoku) No. S63-56122 and Japanese Patent Application Laid-Open (Kokai) No. H4-346446.
A bonding apparatus 20, such as a wire bonding apparatus, die bonding apparatus, etc. is installed on one side of the guide rails 11 so as to face the bonding position 15. This bonding apparatus 20 has an XY table 21 which is driven in the X and Y directions, and a bonding head 22 is mounted on this XY table 21. In addition, a camera holder 24 to which a television camera 23 is attached is fastened to the bonding head 22. Furthermore, a bonding arm 26 to which a bonding tool 25 is attached is installed on the bonding head 22 so that the bonding arm 26 can be moved up and down along the two-dotted line in FIG. 4(b). The television camera 23 is positioned so as to be above the bonding position 15, as best seen from FIG. 4(b), and the bonding tool 25 is offset by a distance of Y1 from the television camera 23 as shown in FIG. 4(a). The bonding arm 26 is raised and lowered by a Z (vertical) driving motor (not shown).
One example of a bonding apparatus 20 of this type is described in Japanese Patent Application Laid-Open (Kokai) No. H5-275502.
With the apparatus described above, lead frames 6 inside the loader side magazines 1 are pushed out by the frame pusher 7 to a position where the lead frames 6 can be chucked by the loader side feeding claws 12. Afterward, the frame pusher 7 returns to its original position.
There are two types of pull-in claws 8 which pull out the lead frames 6: one type inserts a pull-out pin into each lead frame 6, and another type chucks each lead frame 6 from above and below.
In the case of the type which inserts a pull-out pin, the pull-in claw 8 is moved into the loader side magazine 1 and then lowered so that the pull-out pin is inserted into a hole (not shown) of a lead frame 6. Next, the pull-in claw 8 is moved in the feeding direction (toward the bonding position 15, rightward in FIGS. 4(a) and 4(b)) so as to pull out the lead frame 6 from the magazine 1 to the position 15 where the lead frame 6 can be chucked by the loader side feeding claws 12. Afterward, the pull-in claw 8 is raised and returns to its original position.
In the case of the type which chucks each lead frame from above and below to take out the lead frames, the pull-in claw 8 holding a lead frame 6 from above and below pulls the lead frame 6 out of the loader side magazine 1, and then the loader side feeding claws 12 hold the lead frame 6 and transfer the lead frame 6 to the bonding position 15.
When the frame confirmation sensor 14 detects the presence of the lead frame 6 thus taken out by either the frame pusher 7 or the claw 8 onto the guide rails 1, the loader side feeding claws 12 close and chuck the lead frame 6 and then intermittently feed the lead frame 6 along the frame conveying path 11 a of the guide rails 11. In other words, an intermittent feeding action is repeated so that the loader side feeding claws 12 open, return to their original position, close and chuck the lead frame 6, and again feed the lead frame 6 by a fixed amount. The bonding portions of the lead frame 6 are thus successively fed to the bonding position 15.
Each time a bonding portion of the lead frame 6 is fed to the bonding position 15, bonding is performed by the bonding apparatus 20. After the bonding is completed, the lead frame 6 is intermittently fed by the unloader side feeding claws 13 and is stored in the unloader side magazine 2.
In the above operation, the lead frames 6 are stored in a stacked configuration with a fixed spacing in the loader side magazines 1 and unloader side magazines 2. Accordingly, each time that a lead frame 6 is supplied to the frame conveying path 11a of the guide rails 11 from one of the loader side magazines 1, and each time a lead frame 6 is transferred into one of the unloader side magazines 2 from the conveying path 11a, the loader side magazine 1 and unloader side magazine 2 are lowered by one pitch, so that the frame storing section of the loader side magazine 1 or unloader side magazine 2 which stores or is to store the next lead frame 6 is positioned at the conveying path level of the frame conveying path 11a. The "conveying path level" of the frame conveying path 11 a refers to a height suitable for feeding a lead frame 6 onto the frame conveying path 11a.
In a system where two or more loader side magazines 1 (1A, 1B . . . ) and unloader side magazines 2 (2A, 2B . . . ) are stacked on the magazine holders 5 of the loader side elevator 3 and unloader side elevator 4, after the lead frame 6 in the uppermost frame storing section of one loader side magazine 1 has been fed out at the conveying path level of the frame conveying path 11a, or after a lead frame 6 has been stored in the uppermost frame storing section of one unloader side magazine 2, the loader side magazine 1 or unloader side magazine 2 is lowered so that the lowermost frame storing section of the loader side magazine 1 or unloader side magazine 2 positioned immediately above the loader side magazine 1 or unloader side magazine 2 is positioned at the conveying path level of the frame conveying path 11a.
In ordinary production plan, the lead frames 6 are controlled in lots; however, one lot hardly ever consists of a number of lead frames 6 equal to the number of frame storing sections times one loader side magazine (the number of frame storing sections.times.N (where N is the number of loader side magazines 1)). Accordingly, the last loader side magazine 1 of one lot is not always completely filled with lead frames 6. FIG. 4(b) illustrates a case wherein the loader side magazine 1B is the last magazine of one lot; and four frame storing sections of the magazine 1B are empty. In FIG. 4(b), in order to facilitate understanding, frame storing sections which do not contain lead frames are shown by two-dot chain lines.
In this situation, the loader side magazines 1 (1A, 1B . . . ) are lowered one stage at a time by the loader side elevator 3; and each time the magazines are lowered, a push-out operation is performed by the frame pusher 7 or a pull-in operation is performed by the pull-in claw 8, regardless of whether or not a lead frame 6 is on the stage (or in the storing section) of the loader side magazine 1 (1A, 1B, etc.). Then, when a pre-set number of stages (stored in a memory) is reached, the loader side magazine 1 (1A, 1B, etc.) is removed; and the first stage of the next magazine is positioned at the conveying path level of the frame conveying path 11a, thus continuing the lead frame supply operations.
As seen from the above, in the case of the loader side magazine which is the last magazine of a lot, the frame pusher or pull-in claw goes through the feeding out operation even though the lead frame storing sections do not contain a lead frame. During this period, no lead frames are supplied to the frame conveying path 11a. In other words, the bonding apparatus 20 cannot perform bonding and is therefore placed in waiting, making productivity poor.